Sex appeal is a rare commodity in the world of science, but Ugo Amaldi, an Italian physicist, has it in abundance. Although he has lived and worked in Geneva for the past 13 years, the rigours of the Swiss winter have not yet bleached the last traces of Mediterranean sun from his face nor has the town's dour Calvinism ironed out the laughter lines around his eyes. Perhaps only the greying of his hair makes credible his assertion that 'I am not far off 60 and would be too old' for the next great experiment in his branch of science.

Since 1980 he has been spokesman for the hundreds of scientists working on the so-called 'Delphi' experiment at Cern, the European Laboratory for Particle Physics, on the Franco-Swiss border near Geneva. Delphi is one of four massive installations, each larger than a semi-detached house, which try to grasp and record the fleeting lives of the subnuclear particles brought briefly into existence as Cern's biggest and most powerful particle accelerator, known as Lep, recreates conditions unknown in the universe since the Big Bang some 15 billion years ago.

But while Professor Amaldi has an intimate grasp of the details of the experiments, he is characteristically Latin in his fondness for the grander picture. It is an approach that makes a refreshing contrast to the cautious pragmatism of British researchers. 'There are three problems which interest people,' he said. 'The origin of the universe; the origin of life; and the origin of the mind.' Everyone wants to know, he continued, why we are here and why the universe is here. 'At Cern, we address the question of why the universe is here.'

A pause, the hint of a twinkle in the eye, and then: 'I am here to study nothing - the vacuum.' More than 9,500 people work at Cern - some 3,000 of them permanently employed there, the rest are visiting physicists - and the laboratory costs the European taxpayer about SwFr950m ( pounds 436m) a year to run. All that money, all that scientific talent, to study the emptiness of the void.

Well, not quite. For Professor Amaldi, the study of the void is the study of the origins of the universe because 'the universe originated from the vacuum'. And, in any case, 'the physical vacuum is not the same as the metaphysical nothing. The physical nothing is full of things'. These are not the hard billiard-ball particles we picture to ourselves,

but the underlying fields pregnant with the potential for assuming the forms of existence we do recognise.

To study nothingness out of which everything has been spun: that is the rationale of Cern. That is why, on Friday, Europe's physicists hope to put before their political masters a plan to build a new machine, at a cost of more than SwFr2bn, over the next decade. It will be the successor to Lep, the next great experiment in fundamental physics and the one which Professor Amaldi thinks he is too old for and should be left to younger men: the large hadron collider, or LHC.

Daniel Froidevaux is of that younger generation. A 39-year-old Frenchman, he is designing one of the two detectors that will track the particles created in LHC. His detector is known as Atlas; its counterpart has the more boring sobriquet of CMS. Each experiment will cost about SwFr400m - in addition to the SwFr2bn the LHC itself will cost.

The LHC will be a subterranean racetrack for protons - the nuclei of hydrogen, the simplest of all atoms - and their anti-matter counterparts, anti-protons. The accelerator will sit on top of Lep inside the 27-kilometre (17-mile) tunnel which runs in a loop from deep under the Jura mountains towards Lake Geneva and back again.

If Europe's political paymasters agree to it, the LHC will be a stupendous feat of precision engineering employing the exotic and difficult technology of superconductivity on a massive scale. In obedience to Newton's laws of motion, the protons would like to move in a straight line, so 5,000 powerful superconducting magnets, each 13 metres (42.5ft) long, will be needed to bend their path into a closed circle and to focus the beams. As they circle, the protons will pass through radio-frequency cavities - like sophisticated microwave ovens - and just as a microwave oven imparts energy to food, so the protons will pick up energy in these accelerating cavities. Essentially they will 'surf' on the radio waves, drawing energy to increase their speed.

But for all its technological wizardry, the LHC will be just a factory to produce particles. As the protons and their anti-proton counterparts collide, they will annihilate in a flash of pure energy, corresponding to temperatures which have not existed in the cosmos since a fraction of a second after the Big Bang. As the fire of the explosion cools, the energy will condense into myriad subnuclear particles whose behaviour will carry the imprint of the forces at work in the moment of annihilation - and thus of the forces at work during the universe's creation.

Atlas, the instrument that Dr Froidevaux and his colleagues are designing, will pick up the tracks of these particles and reconstruct the forces that shaped them. Atlas is itself a technological tour de force. It will be 40 metres long and 20 metres in diameter. It will pick up 1 million billion interactions in a year, yet will be able to select perhaps just 10 which are particularly interesting.

By the end of 1995, Dr Froidevaux expects that the physicists will have finalised their plans for what they want Atlas to do. Thereafter, it will be an engineering project until, in about 2003, the LHC starts up and the data begins to flow. Dr Froidevaux is philosophical about the snail's pace of advance in his branch of science: 'I will be almost 50 when the LHC starts, so it will be my last experiment as an active physicist.'

Cern is now the world's largest scientific research organisation. With the decision by the US Congress to cancel the American Superconducting Supercollider project, the LHC would ensure that Europe dominates fundamental particle physics for the foreseeable future. The man who has to sell the project to the Treasuries of 19 cash-strapped European nations is British. A theoretician, on leave of absence from the professorship of physics at Oxford, Christopher Llewellyn Smith takes over as director-general of Cern on 1 January.

He looks surprisingly boyish for a man of 51, a legacy perhaps of his successful combination of academic brilliance with a full Blue for athletics as a student at Oxford. He may not dress with Italian style, but he brings to his new job the expertise of a front rank physicist together with the tact and social skills of an international diplomat - for it is the DG's job to keep the member states sweet while keeping the respect of the lab's scientists.

On Friday, Professor Llewellyn Smith will put forward his vision of how Europe's scientists can peer into the entrails of the smallest and most short-lived objects in creation and see the birth of the universe reflected there. A price tag of SwFr2bn seems rather cheap for all that.